The present invention relates to a method for joining a joining component to a workpiece, and to a joining apparatus, in particular for carrying out a joining method as disclosed herein.
In general, the present invention relates to the field of joining of joining components, such as attachment elements, to workpieces such as bodywork components. In this case, an attachment element such as this generally has two functional sections, firstly a flange section by means of which the connection can be made to the workpiece. Secondly, the joining component in general has a holding section which, for example, may be in the form of an attachment shaft in order to fix further attachment elements, such as plastic clips, thereto.
Joining components such as these have been known for a long time as welding studs composed of metal, which are welded to workpieces such as metal bodywork sheets by means of so-called stud welding. This type of attachment has the advantage that a welding stud such as this can be welded onto the workpiece even when the latter is accessible from only one side.
It is also known for metal studs such as these to be adhesively bonded to a metal bodywork sheet. In this case, a joining surface of a flange section of the stud is provided with thermoplastic adhesive which can be activated by heating the stud, in order to form a force-fitting adhesive connection with the surface of the workpiece. An apparatus for stud adhesion is, for example, known from the document DE 10 2004 012 786 A1. In this case, the stud is held by means of a holding apparatus and is heated by means of an induction coil which is arranged coaxially with respect to a shank section of the bolt that is being held. Furthermore, a carriage which is provided on the joining apparatus can be moved towards the workpiece by means of a linear drive, in order to press the stud onto the workpiece. When the adhesive is activated and liquefied, an adhesive bead is formed around the outer rim of the flange section.
In a similar apparatus (U.S. Pat. No. 4,355,222), the stud is placed on the workpiece in advance, and is then pressed against the workpiece by means of a joining tool, while the adhesive is being activated.
Document DE 10 2006 059 337 A1 discloses a method for connection of parts composed of thermoplastic material wherein a joining component in the form of a holder is joined to a vehicle bumper bar composed of plastic. A connection element which has apertures, projections and/or depressions is arranged between the surfaces of the parts to be connected to one another. The connection element is designed to be heated when a varying magnetic field is applied. In consequence, the thermoplastic material of the surfaces is melted. When the molten material solidifies, this leads to a connection at least between the surfaces and the connection element, and thus to a connection between the parts via the connection element. The connection element can be joined onto one of the parts to be connected, in advance. Furthermore, the connection element is inductively heated via an induction heating device, which is arranged on the side of the workpiece opposite the joining component during the joining process.